Thick film conductors serve as electrical interconnections between resistors, capacitors and integrated circuits. Thick film conductors are used in the microcircuit industry to "terminate" resistor or capacitor patterns, typically by firing the conductor pattern on a substrate and then printing the resistor or capacitor pattern over part of the conductor pattern and then firing them both.
Similarly to other thick film materials, thick film conductors are comprised of an active (conductive) metal and inorganic binder, both of which are in finely divided form and are dispersed in an organic vehicle. The conductive phase is ordinarily gold, palladium, silver, platinum or alloys thereof, the choice of which depends upon the particular performance characteristics which are sought, e.g., resistivity, solderability, solder leach resistance, migration resistance, bondability and the like.
Thick film techniques are contrasted with thin film techniques which involve deposition of particles by evaporation or sputtering. Thick film techniques are discussed in Handbook of Materials and Processes for Electronics, C. A. Harper, Editor, McGraw-Hill, N.Y., 1970, Chapter 12.
In addtion to the proper level of conductivity there are many secondary properties which must also be present such as good adhesion to both ceramic substrates and thick films, solderability and compatibility to other thick films little or no surface crystal growth and good capability of use in hermetic systems and little or no chemical interaction with overprinted thick film resistor or capacitor systems.
As would be expected, a most critical variable in the technology of thick film conductors for use as terminations is the adhesion of the two functional systems. Thus, there has been emphasis in the prior art on the addition of various adhesion promoters. Of particular importance in this regard has been the incorporation of titanium resonate (organic titanates) into thick film dielectric compositions to effect better adhesion both to the substrate and to the thick film terminations with which they are used. In this application relative adhesion is observed by the tenacity of the termination to peel away from the dielectric material after the system is fired.